U.S. patent number 9,857,572 [Application Number 15/234,502] was granted by the patent office on 2018-01-02 for fixed-focus projection lens.
This patent grant is currently assigned to CALIN TECHNOLOGY CO., LTD.. The grantee listed for this patent is CALIN TECHNOLOGY CO., LTD.. Invention is credited to Po-Nien Tsai, Chien Hsiung Tseng, Yi-Ling Yang.
United States Patent |
9,857,572 |
Tseng , et al. |
January 2, 2018 |
Fixed-focus projection lens
Abstract
A fixed-focus projection lens, in order from an image side to an
image source side along an optical axis, includes a first lens with
negative refractive power, a second lens with positive refractive
power, a third lens with negative refractive power, a fourth lens
with positive refractive power, a fifth lens with positive
refractive power, and a sixth lens with positive refractive power.
The second lens is a biconvex lens. While projecting, a light
enters the fixed-focus projection lens from the image source side,
and passes through the fixed-focus projection lens. Further more,
at least one surface of the first lens is aspherical, a refractive
index of the second lens is greater than 1.8, and a refractive
index of the fifth lens is greater than 1.7. Such arrangement helps
to lower a spherical aberration of spherical lens, shortening the
optical system, and effectively lower the distortion.
Inventors: |
Tseng; Chien Hsiung (Hsinchu,
TW), Yang; Yi-Ling (Taichung, TW), Tsai;
Po-Nien (Pingtung County, TW) |
Applicant: |
Name |
City |
State |
Country |
Type |
CALIN TECHNOLOGY CO., LTD. |
Taichung |
N/A |
TW |
|
|
Assignee: |
CALIN TECHNOLOGY CO., LTD.
(Taichung, TW)
|
Family
ID: |
60483780 |
Appl.
No.: |
15/234,502 |
Filed: |
August 11, 2016 |
Prior Publication Data
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|
|
|
Document
Identifier |
Publication Date |
|
US 20170351068 A1 |
Dec 7, 2017 |
|
Foreign Application Priority Data
|
|
|
|
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Jun 2, 2016 [TW] |
|
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105117396 A |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02B
13/0045 (20130101); G02B 9/60 (20130101); G02B
27/0025 (20130101); G02B 5/005 (20130101); G02B
13/16 (20130101) |
Current International
Class: |
G02B
9/00 (20060101); G02B 27/00 (20060101); G02B
13/16 (20060101); G02B 5/00 (20060101); G02B
13/00 (20060101); G02B 9/60 (20060101) |
Field of
Search: |
;359/649-651,713,752,756 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Choi; William
Attorney, Agent or Firm: Wylie; Lynette Apex Juris, pllc
Claims
What is claimed is:
1. A fixed-focus projection lens, in order from an image side to an
image source side along an optical axis, comprises a first lens, a
second lens, a third lens, a fourth lens, a fifth lens, and a sixth
lens, wherein, while projecting, a light enters the fixed-focus
projection lens from the image source side, and passes through the
fixed-focus projection lens to the image side, wherein: the first
lens has a negative refractive power; the second lens is a biconvex
lens with a positive refractive power; the third lens has a
negative refractive power; the fourth lens has a positive
refractive power; the fifth lens has a positive refractive power;
and the sixth lens has a positive refractive power; wherein the
third lens and the fourth lens are adhered together to form a
doublet lens with negative refractive power.
2. The fixed-focus projection lens of claim 1, wherein the first
lens is a negative meniscus, and a convex surface thereof faces the
image side; the third lens is a biconcave lens; the fourth lens is
a biconvex lens; the fifth lens is a biconvex lens; the sixth lens
is a meniscus lens.
3. The fixed-focus projection lens of claim 2, wherein at least one
surface of the first lens is aspherical; at least one surface of
the sixth lens is aspherical.
4. The fixed-focus projection lens of claim 3, wherein both
surfaces of the first lens and both surfaces of the sixth lens are
aspherical.
5. The fixed-focus projection lens of claim 4, wherein both
surfaces of the second lens, the third lens, the fourth lens, and
the fifth lens are spherical.
6. The fixed-focus projection lens of claim 3, wherein both
surfaces of the second lens, the third lens, the fourth lens, and
the fifth lens are spherical.
7. The fixed-focus projection lens of claim 3, wherein the third
lens and the fourth lens are adhered together to form a doublet
lens with negative refractive power.
8. The fixed-focus projection lens of claim 7, wherein the doublet
lens satisfies the following conditions:
-2.02.ltoreq.fc/f.ltoreq.-1.78, where f is a focal length of the
fixed-focus projection lens, and fc is a focal length of the
doublet lens.
9. The fixed-focus projection lens of claim 3, wherein a distance
between the third lens and the fourth lens is smaller than a
distance between each adjacent lens of the fixed-focus projection
lens.
10. The fixed-focus projection lens of claim 3, wherein a radius of
curvature of different segments on the at least one surface of the
sixth lens is different.
11. The fixed-focus projection lens of claim 10, wherein the radius
of curvature of the at least one surface of the sixth lens
decreases gradually from where the optical axis passes through to a
side of the sixth lens.
12. The fixed-focus projection lens of claim 2, wherein the third
lens and the fourth lens are adhered together to form a doublet
lens with negative refractive power.
13. The fixed-focus projection lens of claim 12, wherein the
doublet lens satisfies the following conditions:
-2.02.ltoreq.fc/f.ltoreq.-1.78; where f is a focal length of the
fixed-focus projection lens, and fc is a focal length of the
doublet lens.
14. The fixed-focus projection lens of claim 2, wherein a distance
between the third lens and the fourth lens is smaller than a
distance between each adjacent lens of the fixed-focus projection
lens.
15. The fixed-focus projection lens of claim 2, wherein a radius of
curvature of different segments on the at least one surface of the
sixth lens is different.
16. The fixed-focus projection lens of claim 15, wherein the radius
of curvature of the at least one surface of the sixth lens
decreases gradually from where the optical axis passes through to a
side of the sixth lens.
17. The fixed-focus projection lens of claim 2, wherein a
refractive index of the fifth lens is greater than 1.7.
18. The fixed-focus projection lens of claim 1, wherein the doublet
lens satisfies the following conditions:
-2.02.ltoreq.fc/f.ltoreq.-1.78; where f is a focal length of the
fixed-focus projection lens, and fc is a focal length of the
doublet lens.
19. The fixed-focus projection lens of claim 1, wherein a distance
between the third lens and the fourth lens is smaller than a
distance between each adjacent lens of the fixed-focus projection
lens.
20. The fixed-focus projection lens of claim 1, wherein a radius of
curvature of different segments on the at least one surface of the
sixth lens is different.
21. The fixed-focus projection lens of claim 20, wherein the radius
of curvature of the at least one surface of the sixth lens
decreases gradually from where the optical axis passes through to a
side of the sixth lens.
22. The fixed-focus projection lens of claim 1, wherein the
fixed-focus projection lens satisfies the following condition:
-1.74.ltoreq.f1/f.ltoreq.-1.60; where f is a focal length of the
fixed-focus projection lens, and f1 is a focal length of the first
lens.
23. The fixed-focus projection lens of claim 1, wherein the
fixed-focus projection lens satisfies the following condition:
2.02.ltoreq.f2/f.ltoreq.2.17; where f is a focal length of the
fixed-focus projection lens, and f2 is a focal length of the second
lens.
24. The fixed-focus projection lens of claim 1, wherein the
fixed-focus projection lens satisfies the following condition:
-0.85.ltoreq.f3/f.ltoreq.-0.80; where f is a focal length of the
fixed-focus projection lens, and f3 is a focal length of the third
lens.
25. The fixed-focus projection lens of claim 1, wherein the
fixed-focus projection lens satisfies the following condition:
1.66f4/f.ltoreq.1.81; where f is a focal length of the fixed-focus
projection lens, and f4 is a focal length of the fourth lens.
26. The fixed-focus projection lens of claim 1, wherein the
fixed-focus projection lens satisfies the following condition:
1.81.ltoreq.f5/f.ltoreq.1.89; where f is a focal length of the
fixed-focus projection lens, and f5 is a focal length of the fifth
lens.
27. The fixed-focus projection lens of claim 1, wherein the
fixed-focus projection lens satisfies the following condition:
3.33.ltoreq.f6/f.ltoreq.3.50; where f is a focal length of the
fixed-focus projection lens, and f6 is a focal length of the sixth
lens.
28. The fixed-focus projection lens of claim 1, wherein a
refractive index of the second lens is greater than 1.8.
29. The fixed-focus projection lens of claim 28, wherein a
refractive index of the fifth lens is greater than 1.7.
30. The fixed-focus projection lens of claim 1, further comprises
an aperture provided between the second lens and the third lens.
Description
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention generally relates to projection lens, and
more particularly to a fixed-focus projection lens.
2. Description of Related Art
In recent years, with advantages in technology, it becomes more
popular to use a projector to give presentations, hold a video
conference, or watch television programs. Various kinds of small
and lightweight projectors are designed and manufactured in pursuit
of better portability and easier use, and therefore, the size of
the lens used in a projector is demanded to become smaller.
With the development of high resolution in projection technology,
the lens of projector is required to provide higher image quality
and lower distortion. However, in order to achieve the required
performance, a lens either has to include more than ten lenses for
compensation, leading to a bulky and heavy projector, or has to use
a lens with greater processing difficulty. Such solutions seem to
contradict with the trend of miniaturization.
BRIEF SUMMARY OF THE INVENTION
In view of the reasons mentioned above, the primary objective of
the present invention is to provide a fixed-focus projection lens,
of which the total length is short, and has an optical performance
of high image quality and low distortion.
The present invention provides a fixed-focus projection lens,
which, in order from an image side to an image source side along an
optical axis, comprises a first lens, a second lens, a third lens,
a fourth lens, a fifth lens, and a sixth lens, wherein, while
projecting, a light passes intoenters the fixed-focus projection
lens through from the image source side, and passes out ofthrough
the fixed-focus projection lens through to the image side. The
first lens has a negative refractive power. The second lens is a
biconvex lens with a positive refractive power. The third lens has
a negative refractive power. The fourth lens has a positive
refractive power. The fifth lens has a positive refractive power;
and the sixth lens has a positive refractive power.
In an embodiment, the first lens is a negative meniscus, and a
convex surface thereof faces the image side; the third lens is a
biconcave lens; the fourth lens is a biconvex lens; the fifth lens
is a biconvex lens; the sixth lens is a meniscus lens.
In an embodiment, at least one surface of the first lens is
aspherical; at least one surface of the sixth lens is
aspherical.
In an embodiment, both surfaces of the first lens and both surfaces
of the sixth lens are aspherical.
In an embodiment, both surfaces of the second lens, the third lens,
the fourth lens, and the fifth lens are spherical.
In an embodiment, the third lens and the fourth lens are adhered
together to form a doublet lens with negative refractive power.
In an embodiment, the doublet lens satisfies the following
conditions: -2.02.ltoreq.fc/f.ltoreq.-1.78; where f is a focal
length of the fixed-focus projection lens, and fc is a focal length
of the doublet lens.
In an embodiment, a distance between the third lens and the fourth
lens is smaller than a distance between each adjacent lens of the
fixed-focus projection lens.
In an embodiment, a radius of curvature of different segments on
the at least one surface of the sixth lens is different.
In an embodiment, the radius of curvature of the at least one
surface of the sixth lens decreases gradually from where the
optical axis passes through to a side of the sixth lens.
In an embodiment, the fixed-focus projection lens satisfies the
following condition: -1.74.ltoreq.f1/f.ltoreq.-1.60; where f is a
focal length of the fixed-focus projection lens, and f1 is a focal
length of the first lens.
In an embodiment, the fixed-focus projection lens satisfies the
following condition: 2.02.ltoreq.f2/f.ltoreq.2.17; where f is a
focal length of the fixed-focus projection lens, and f2 is a focal
length of the second lens.
In an embodiment, the fixed-focus projection lens satisfies the
following condition: -0.85.ltoreq.f3/f.ltoreq.-0.80; where f is a
focal length of the fixed-focus projection lens, and f3 is a focal
length of the third lens.
In an embodiment, the fixed-focus projection lens satisfies the
following condition: 1.66.ltoreq.f4/f.ltoreq.1.81; where f is a
focal length of the fixed-focus projection lens, and f4 is a focal
length of the fourth lens.
In an embodiment, the fixed-focus projection lens satisfies the
following condition: 1.81.ltoreq.f5/f.ltoreq.1.89; where f is a
focal length of the fixed-focus projection lens, and f5 is a focal
length of the fifth lens.
In an embodiment, the fixed-focus projection lens satisfies the
following condition: 3.33.ltoreq.f6/f.ltoreq.3.50; where f is a
focal length of the fixed-focus projection lens, and f6 is a focal
length of the sixth lens.
In an embodiment, a refractive index of the second lens is greater
than 1.8.
In an embodiment, a refractive index of the fifth lens is greater
than 1.7.
In an embodiment, an aperture provided between the second lens and
the third lens.
With the aforementioned design, the fixed-focus projection lens of
the present invention could achieve the effect of high image
quality and low distortion. In addition, the number of the lens of
the fixed-focus projection lens is limited to six, which reduces
the volume and helps to keep the fixed-focus projection lens
miniaturized and lightweight. Furthermore, the fixed-focus
projection lens of the present invention could be easily
manufactured and assembled.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
The present invention will be best understood by referring to the
following detailed description of some illustrative embodiments in
conjunction with the accompanying drawings, in which
FIG. 1 is a schematic diagram of a first embodiment of the present
invention;
FIG. 2A is a diagram showing the field curvature of the first
embodiment;
FIG. 2B is a diagram showing the distortion of the first
embodiment;
FIG. 2C is a diagram showing the longitudinal spherical aberration
of the first embodiment;
FIG. 2D is a diagram showing the focus shift of the first
embodiment;
FIG. 3 is a schematic diagram of a second embodiment of the present
invention;
FIG. 4A is a diagram showing the field curvature of the second
embodiment;
FIG. 4B is a diagram showing the distortion of the second
embodiment;
FIG. 4C is a diagram showing the longitudinal spherical aberration
of the second embodiment;
FIG. 4D is a diagram showing the focus shift of the second
embodiment;
FIG. 5 is a schematic diagram of a third embodiment of the present
invention;
FIG. 6A is a diagram showing the field curvature of the third
embodiment;
FIG. 6B is a diagram showing the distortion of the third
embodiment;
FIG. 6C is a diagram showing the longitudinal spherical aberration
of the third embodiment; and
FIG. 6D is a diagram showing the focus shift of the third
embodiment.
DETAILED DESCRIPTION OF THE INVENTION
A fixed-focus projection lens 1 of a first embodiment of the
present invention is illustrated in FIG. 1; a fixed-focus
projection lens 2 of a second embodiment of the present invention
is illustrated in FIG. 3, and a fixed-focus projection lens 3 of a
third embodiment of the present invention is illustrated in FIG. 5.
Each of the aforementioned fixed-focus projection lens 1, 2, 3 has
a first lens L1, a second lens L2, a third lens L3, a fourth lens
L4, a fifth lens L5, and a sixth lens L6, which are arranged in
order from an image side to an image source side along an optical
axis Z. While projecting, a light enters the fixed-focus projection
lens from the image source side, passes through each fixed-focus
projection lens 1, 2, 3, and eventuall arrives at the image side.
Furthermore, to meet different requirements, an aperture ST is
provided between the second lens L2 and the third lens L3, and a
prism P is provided behind the sixth lens L6 (i.e., near the image
source side), and therefore enhances the optical quality.
The first lens L1 has negative refractive power. Preferably, the
first lens L1 of each of the three embodiments of the present
invention is a meniscus with negative refractive power, wherein a
convex surface S1 thereof faces the image side, while a concave
surface S2 thereof faces the image source side. Furthermore, at
least one surface of the first lens L1 is aspherical. Preferably,
both sides of the first lens L1 of each of the three embodiments of
the present invention are aspherical. Since the surface of an
aspherical lens is curved, it helps to lower a spherical aberration
which might happen for a spherical lens, and to reduce the number
of lens. Whereby, the lens quality could be enhanced, the optical
system could be shortened, and the distortion could be effectively
lowered.
The second lens L2 is a biconvex lens with positive refractive
power. Preferably, a refractive index of the second lens L2 of each
of the three embodiments of the present invention is greater than
1.8. The higher refractive index is, the thinner lens would be. In
this way, a weight of the fixed-focus projection lens 1, 2, 3 could
be lighter, and a volume of the fixed-focus projection lens 1, 2, 3
could be reduced.
The third lens L3 has negative refractive power, and the fourth
lens L4 has positive refractive power, wherein a distance between
the third lens L3 and the fourth lens L4 is less than a distance
between any two adjacent lens in the fixed-focus projection lens.
Preferably, the third lens L3 of each of the three embodiments of
the present invention is a biconcave lens, while the fourth lens L4
of each of the three embodiments of the present invention is a
biconvex lens. The third lens L3 and the fourth lens L4 are adhered
together to form a doublet lens with negative refractive power.
With the doublet lens and others lenses, an axial chromatic
aberration could be effectively eliminated.
The fifth lens L5 has positive refractive power. Preferably, the
fifth lens L5 of the three embodiments of the present invention is
a biconvex lens, wherein a refractive index of the fifth lens L5 is
greater than 1.7. The higher refractive index is, the thinner lens
would be. In this way, the weight of the fixed-focus projection
lens 1, 2, 3 could be lighter, and the volume of the fixed-focus
projection lens 1, 2, 3 could be reduced.
The sixth lens L6 has positive refractive power. Preferably, the
sixth lens L6 of each of the three embodiments of the present
invention is a meniscus lens, which includes at least one
aspherical surface, wherein a concave surface S11 thereof faces the
image side, and a value of a radius of curvature of the concave
surface decreases gradually from where the optical axis Z passes
through to a side of the sixth lens L6. Whereby, an incident angle
of a chief ray entering the image side could be decreased, and the
spherical aberration and a stigmatism could be reduced, which could
increase a discernibility of the fixed-focus projection lens. The
convex surface S12 faces the image source side, which helps to
lower an aberration.
In order to effectively enhance the optical quality of the
fixed-focus projection lens, the effective focal length (EFL) at
where the optical axis Z passes through, a F number (Fno) of the
aperture, a distortion, a radius of curvature (R), a distance (D)
between each surface and the next surface on the optical axis Z, a
refractive index (Nd) of each lens, an Abbe number (Vd) of each
lens, half of the effective aperture of each surface, and a focal
length of each of the fixed-focus projection lenses 1, 2, 3 of the
three embodiments on the present invention are respectively listed
in the following Table 1 to Table 3.
TABLE-US-00001 TABLE 1 EFL = 16.735 mm; Fno = 1.4 Half of the Focal
Effective length Surface R(mm) D(mm) Nd Vd Aperture (mm) (mm) Note
S1 137.2502 2.67918 1.525279 55.95076 31.02808 -27.922 First lens
L1 S2 13.20725 27.03838 24.9 S3 33.97213 4.225561 1.834000 37.16049
24.7 34.597 Second lens L2 S4 -187.736 10.93017 24.4 S5 Infinity
10.29608 20.6203 Aperture ST S6 -20.8406 3.720065 1.784723 25.68345
18.5 -13.863 Third lens L3 S7 24.97922 7.16298 1.618000 63.3335
22.6 29.197 Fourth lens L4 S8 -58.5681 0.22863 24.1 S9 52.27049
6.060089 1.772499 49.59837 26.93156 30.996 Fifth lens L5 S10
-42.2814 0.670936 27.3 S11 -1977.21 6.877584 1.525279 55.95076
27.12 56.633 Sixth lens L6 S12 -29.4531 9.91922 28.5 S13 Infinity
25.75 1.516800 64.16734 24.13676 Prism P S14 Infinity 0.1 18.98573
S15 Infinity 0.023972 18.95545 Image source S16 Infinity
18.94819
TABLE-US-00002 TABLE 2 EFL = 16.941 mm; Fno = 1.4 Half of the Focal
Effective length Surface R(mm) D(mm) Nd Vd Aperture (mm) (mm) Note
S1 137.2502 2.67918 1.525279 55.95076 31.02943 -27.921 First lens
L1 S2 13.20725 27.03838 24.9 S3 33.97213 4.225561 1.834 37.16049
24.7 34.619 Second lens L2 S4 -187.736 10.93017 24.4 S5 Infinity
10.29608 20.6203 Aperture ST S6 -20.8406 3.720065 1.784723 25.68345
18.5 -13.901 Third lens L3 S7 24.97922 7.16298 1.618 63.3335 22.6
30.278 Fourth lens L4 S8 -58.5681 0.22863 24.1 S9 52.27049 6.060089
1.772499 49.59837 26.93156 31.006 Fifth lens L5 S10 -42.2814
0.670936 27.3 S11 -1977.21 6.877584 1.525279 55.95076 27.12 56.66
Sixth lens L6 S12 -29.4531 9.91922 28.5 S13 Infinity 25.75 1.5168
64.16734 24.13888 Prism P S14 Infinity 0.1 18.98578 S15 Infinity
0.023972 18.95548 Image source S16 Infinity 18.94822
TABLE-US-00003 TABLE 3 EFL = 16.458 mm; Fno = 1.4 Half of the Focal
Effective length Surface R(mm) D(mm) Nd Vd Aperture (mm) (mm) Note
S1 129.0124 3.705238 1.525160 56.281538 31.75174 -28.226 First lens
L1 S2 13.20766 27.59851 -0.36042 S3 35.02584 4.400845 1.834000
37.160494 25.10351 34.853 Second lens L2 S4 -166.657 11.62094 24.4
S5 Infinity 9.265208 20.06 Aperture ST S6 -20.794 4.128043 1.784723
25.68344 18.54669 -13.609 Third lens L3 S7 24.2859 6.783116
1.662992 58.165770 22.06738 28.274 Fourth lens L4 S8 -58.0064
0.143169 24.00526 S9 52.40851 5.711219 1.772499 598366 26.6 30.737
Fifth lens L5 S10 -41.6739 0.377883 27.15382 S11 -1196.02 6.212418
1.525120 56.281538 27.13423 56.833 Sixth lens L6 S12 -29.278
10.58329 28.5 S13 Infinity 24.72 1.5168 64.16734 23.91351 Prism P
S14 Infinity 0.1 18.98121 S15 Infinity 0 18.95095 Image source S16
Infinity 18.95095
It can be seen from Table 1 to Table 3 that, the refractive index
of the second lens L2 of each of the fixed-focus projection lens 1,
2, 3 in the three embodiments of the present invention satisfies
the aforementioned condition that the refractive index is greater
than 1.8; the refractive index of the fifth lens L5 satisfies the
aforementioned condition that the refractive index is greater than
1.7.
In addition, an image quality of the fixed-focus projection lens
could be enhanced with the following conditions:
-1.74.ltoreq.f1/f.ltoreq.-1.60; (1) 2.02.ltoreq.f2/f.ltoreq.2.17;
(2) -0.85.ltoreq.f3/f.ltoreq.-0.80; (3)
1.66.ltoreq.f4/f.ltoreq.1.81; (4) 1.81.ltoreq.f5/f.ltoreq.1.89; (5)
3.33.ltoreq.f6/f.ltoreq.3.50; (6) -2.02.ltoreq.fc/f.ltoreq.-1.78.
(7)
Where f is the focal length of the fixed-focus projection lens 1,
2, 3; f1 is a focal length of the first lens L1; f2 is a focal
length of the second lens L2; f3 is a focal length of the third
lens L3; f4 is a focal length of the fourth lens L4; f5 is a focal
length of the fifth lens L5; f6 is a focal length of the sixth lens
L6; fc is a focal length of the doublet lens formed by the third
lens L3 and the fourth lens L4. Where fc of the fixed-focus
projection lens 1 of the first embodiment is -31.441 mm; fc of the
fixed-focus projection lens 2 of the second embodiment is -30.095
mm, and fc of the fixed-focus projection lens 3 of the third
embodiment is -31.54 mm.
The following Table 4 shows a full information of the fixed-focus
projection lens 1, 2, 3 in the three embodiments of the present
invention.
TABLE-US-00004 TABLE 4 Max Min f1/f -1.64 -1.73 f2/f 2.13 2.03 f3/f
-0.81 -0.84 f4/f 1.80 1.73 f5/f 1.88 1.84 f6/f 3.46 3.35 fc/f -1.77
-1.93
Furthermore, a surface concavity Z(y) of each of the aspheric
surfaces S1, S2, S11, S12 in the three embodiments of the present
invention is defined by the following formula:
.function..function..times. ##EQU00001##
where:
Z(y) is the surface concavity (i.e. a variable of the optical axis
varies with y);
y is a height perpendicular to the optical axis;
r is half the off-axis height of the surface;
R is the radius of curvature
K is a conic constant; and
A-G respectively represents different order coefficient of r.
The conic constant k of each of the aspheric surfaces S1, S2, S11,
S12 and each order coefficient A-G of each of the fixed-focus
projection lenses 1, 2, 3 in the three embodiments of the present
invention are respectively listed in the following Tables 5-7.
TABLE-US-00005 TABLE 5 Conic Aspheric surface constant 1 2 11 12 K
0 -0.36145 0 0.374933 A(4th) 1.20E-06 -1.48E-05 -3.42E-05 -7.41E-06
B(6th) -4.12E-08 -1.55E-07 -4.30E-08 -3.11E-08 C(8th) 1.96E-10
3.73E-10 -3.38E-10 -1.86E-10 D(10th) -4.64E-13 -1.60E-12 1.48E-12
7.99E-13 E(12th) 4.57E-16 -1.62E-15 -4.86E-15 -2.14E-15 F(14th) 0 0
0 0 G(16th) 0 0 0 0
TABLE-US-00006 TABLE 6 Conic Aspheric surface constant 1 2 11 12 K
0 -0.36145 0 0.374933 A(4th) 1.20E-06 -1.48E-05 -3.42E-05 -7.41E-06
B(6th) -4.12E-08 -1.55E-07 -4.30E-08 -3.11E-08 C(8th) 1.96E-10
3.73E-10 -3.38E-10 -1.86E-10 D(10th) -4.64E-13 -1.60E-12 1.48E-12
7.99E-13 E(12th) 4.57E-16 -1.62E-15 -4.86E-15 -2.14E-15 F(14th) 0 0
0 0 G(16th) 0 0 0 0
TABLE-US-00007 TABLE 7 Conic Aspheric surface constant 1 2 11 12 K
0 -0.36042 0 0.352917 A(4th) 1.33E-06 -1.40E-05 -3.36E-05 -7.26E-06
B(6th) -4.04E-08 -1.58E-07 -4.45E-08 -3.02E-08 C(8th) 1.93E-10
3.71E-10 -3.34E-10 -1.96E-10 D(10th) -4.81E-13 -1.55E-12 1.50E-12
7.23E-13 E(12th) 5.11E-16 -1.84E-15 -5.55E-15 -2.34E-15 F(14th) 0 0
0 0 G(16th) 0 0 0 0
With the aforementioned design, FIG. 2A shows a diagram of the
field curvature of the first embodiment, wherein a maximum field
curvature thereof does not exceed 0.02 mm and -0.06 mm; FIG. 4A
shows a diagram of the field curvature of the second embodiment,
wherein a maximum field curvature thereof does not exceed 0.02 mm
and -0.06 mm; FIG. 6A shows a diagram of the field curvature of the
third embodiment, wherein a maximum field curvature thereof does
not exceed 0.03 mm and -0.07 mm. It is obvious that the fixed-focus
projection lens of the present invention can effectively lower the
field curvature.
FIG. 2B shows a diagram of a distortion of the first embodiment,
wherein a distortion thereof is from -0.4% to 0.1%; FIG. 4B shows a
diagram of a distortion of the second embodiment, wherein a
distortion thereof is from -0.4% to 0.1%; FIG. 6B shows a diagram
of a distortion of the third embodiment, wherein a distortion
thereof is from -0.4% to 0.1%. It is obvious that the fixed-focus
projection lens of the present invention can effectively control
the distortion.
FIG. 2C shows a diagram of a longitudinal spherical aberration of
the first embodiment, wherein an offset of the longitudinal
spherical aberration thereof is from -0.05 mm to 0.05 mm; FIG. 4C
shows a diagram of a longitudinal spherical aberration of the
second embodiment, wherein an offset of the longitudinal spherical
aberration thereof is from -0.05 mm to 0.05 mm; FIG. 6C shows a
diagram of a longitudinal spherical aberration of the third
embodiment, wherein an offset of the longitudinal spherical
aberration thereof is from -0.05 mm to 0.05 mm. It is obvious that
the fixed-focus projection lens of the present invention can
effectively lower the longitudinal spherical aberration.
FIG. 2D shows a diagram of a focus shift of the first embodiment,
wherein the focus shift thereof is from -20 .mu.m to 60 .mu.m; FIG.
4D shows a diagram of a focus shift of the second embodiment,
wherein the focus shift thereof is from -20 .mu.m to 40 .mu.m; FIG.
6D shows a diagram of a focus shift of the third embodiment,
wherein the focus shift thereof is from -20 .mu.m to 40 .mu.m. It
is obvious that the fixed-focus projection lens of the present
invention can effectively control the focus shift.
In conclusion, with the aforementioned arrangement and optical
conditions, the number of lenses in each of the fixed-focus
projection lenses 1, 2, 3 of the present invention is limited to
six, which helps to keep each of the fixed-focus projection lenses
1, 2, 3 miniaturized and lightweight. In addition, the fixed-focus
projection lens 1, 2, 3 of the present invention could be easily
manufactured and assembled. Furthermore, the fixed-focus projection
lens 1, 2, 3 of the present invention could correct the aberration,
which helps to keep high image quality and low distortion.
It must be pointed out that the embodiments described above are
only some preferred embodiments of the present invention. It is
noted that, the negative meniscus of the first lens L1 is not a
limitation of the present invention, and a biconcave lens with
negative refractive power could be alternatively used as the first
lens L1 to meet different environmental requirements; the biconcave
lens of the third lens L3 is not a limitation of the present
invention, and a negative meniscus with negative refractive power
could be alternatively used as the third lens L3 to meet different
environmental requirements; the biconvex lens of the fourth lens L4
is not a limitation of the present invention, and a meniscus lens
with positive refractive power could be alternatively used as the
fourth lens L4 to meet different environmental requirements; the
biconvex lens of the fifth lens L5 is not a limitation of the
present invention, and a meniscus lens with positive refractive
power could be used as the fifth lens L5 to meet different
environmental requirements; the meniscus lens of the sixth lens L6
is not a limitation of the present invention, and a biconvex lens
with positive refractive power could be alternatively used as the
sixth lens L6. All equivalent structures which employ the concepts
disclosed in this specification and the appended claims should fall
within the scope of the present invention.
* * * * *